Although colorectal carcinoma is a major public health problem in the US with 140,000 new cases annually, there have been no coordinated multi-institutional trials to assess the diagnostic and financial impact on new imaging techniques on patients with this disease. Precise preoperative knowledge of the extent of tumor spread could significantly modify therapy and eliminate unnecessary costly procedures. Knowledge of the optimum protocol to monitor patients with colorectal carcinoma would detect recurrent disease earlier, direct definitive therapeutic procedures, decrease the number of diagnostic tests utilized, and reduce costs. The longterm objective of this research plan is to determine the most effective imaging procedures required to stage and monitor patients with colorectal carcinoma. Our specific aims are to participate in a collaborative group to conduct efficacy studies on diagnostic imaging procedures, to determine the relative sensitivity and specifications of CT, MRI, transrectal and endoscopic ultrasound in staging followup of patients with colorectal carcinoma and to precisely correlate both in vivo and in vitro CT, US, and MRI findings with histologic evaluation of colorectal tumors. ROC curves will be generated and used to determine the relative sensitivities and specificities of each imaging modality for determining the presence, depth of tumor invasion into the wall of the colon, extent of local and distant spread. Exact histologic- imaging correlation will be accomplished using new techniques and instrumentation developed at the University of Washington. Patients with colorectal carcinoma will have CT, MRI, and transrectal or endoscopic US prior to surgery. Rigorous protocols will be followed and observations recorded on forms designed to permit ROC curves to be obtained and analyzed. Each imaging modality will be interpreted prospectively without knowledge of the results of other imaging procedures. Verification of the sensitivity and specificity of imaging procedures will be based on surgical findings and detailed pathologic examination of the resected colorectal carcinoma obtained at the time of initial staging. Postoperatively, patients without disseminated disease will be monitored with CT, MRI, US, and CEA measurements at 6-month intervals for 2 years to determine relative sensitivity and specificities of these procedures in detecting recurrent colorectal carcinoma.